The Stanford academics used the first of those ideas - what's called a Linear No-Threshold (LNT) model.

BBC: Fukushima's disease risk: A major fallout?

The straight-line portion of these types of curves above Earth background has been the basis for the Linear No-Threshold Dose hypothesis, or LNT.

FORBES: Fear Of Radiation -- It's All In The Noise

All dose limits are presently determined by using the Linear No-Threshold dose hypothesis (LNT).

FORBES: Space Invaders -- Asteroids, Mars And Radiation

Brian Lightman, the general secretary of the Association of School and College Leaders, says there is no evidence that linear exams are more rigorous than those taken in modules - and that schools in England should be free to choose which exams their pupils take.

BBC: GCSE changes bring UK differences under devolution

These will also be linear - rather being than taken in "chunks" and there will be no separate "foundation" papers for less academic pupils, where the maximum grade possible is a 'C'.

BBC: Why the Ebacc Certificates sank and what happens next